Photoelectric tube



Patented Sept. l2, 1939 UNITED STATES PATENT OFFICE PHOTOELECTRIC TUBE Paul Grlich, Dresden,

Germany, assigner to Zeiss Ikon Aktiengesellschaft, Dresden, Germany Application October 18, 1937, Serial No.

In Germany October 28, 1936 1 Claim.

The invention relates to improvements in photoelectric tubes and in particular is directed to a photoelectric tube with secondary electron multiplication especially suitable for sound films and television purposes.

It is already known in the art that the light which strikes a photo cathode causes the release of photoelectrons on the latter and that these photoelectrons may be multiplied by conducting the same to one or successively to a number of secondary electron emitting electrodes and nally to a collecting anode.

The principal object of the invention is now a photoelectric tube with secondary electron multiplication of novel and compact construction and having a high sensitiveness and great capacity. According to the invention at least one secondary electron emitting electrode is positioned between the photo cathode and the anode.

Another object of the invention consists in the novel arrangement of a plurality of secondary electron emitting electrodes between the photo cathode and the electron collecting anode.

The manner of accomplishing the foregoing objects and advantages will appear more fully in the following description with reference to the accompanying drawing which shows a sectional view of one embodiment of the photoelectric tube of the invention. ,o 'Ihe inner wall of the envelope I, which for instance may be spherical, has applied thereto a photosensitive layer 2 constituting the photo cathode. This layer 2 is transparent or permeable to light respectively. The anode 3 is ar- 5 ranged in the center of the spherical portion of the envelope I. Between the anode 3 and the photo cathode 2 are positioned a plurality of grid electrodes 4, 5 and 6, each of which is spaced a diierent radial distance from the anode 3 and o extends concentrically about the same. 'I'hese grid electrodes/are provided with coatings which are adapted/to emit secondary electrons.

The electrons emitted by the photo cathode 2 whenl the latter is struck by light travel toward 5 the anode 3 and thereby, encounter iirst the grid electrode 6. This causes the release of sec- (Cl. Z50-166) ondary electrons from the grid electrode 6. These secondary electrons travel also in a direction toward the anode 3 and thereby they strike the next grid electrode 5 to cause again the release of secondary electrons. Another stream of 5 secondary electrons is released from the nextgrid electrode 4 when the electrons on their way to the anode 3 strike this grid electrode. In this manner the electron current released initially from the photo cathode is multiplied a number l0 of times. The voltage between the anode, grid electrodes and cathode are preferably adjusted to yield a relatively high production of secondary electrons. 'Ihe lead-in wires 8, 9, I0, II and I2 connecting the source of potentials with the l5 photo cathode 2, the anode 3, and the grid electrodes 4, 5, 6 respectively may be passed through the base I of the envelope I if the latter consists of glass or the like material.

The photosensitive layer or coatings on the 20 cathode and the grid electrodes consists of conventional materials and are applied in a manner well known in the art.

It is believed obvious that the invention is not limited to the embodiment illustrated by way of example in the drawing, and that modifications in the arrangement and selection of parts, as for instance in the number of grid electrodes may be resorted to, which modications are within the scope of the invention.

What I claim is:

A photoelectric tube, including within a spherical vessel, a transparent photo cathode attached to the inner Wall of said vessel and covering substantially the entire area of said wall, an anode mounted in the center of said spherical vessel, a plurality of spherical grid electrodes mounted each at a different distance from said anode concentrically aboutrthe same, and a lead-in wire for each said grid electrodes the outermost grid 40 electrode being spaced from the wall of said vessel and the photo cathode mounted thereon, said grid electrodes being coated with a substance adapted to emit secondary electrons.

PAUL GORLICH. 

